65 Hydroclimate Variability Across Timescales in Western North America: Causes and Consequences (Posters)

This session aims to bring together researchers studying past climate change over a range of timescales using innovative data and modeling approaches and using these data to inform future changes in climate and their impacts.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Reconstructing Climate Variability in the Pedernales River Basin, Central Texas

Paper number: 65-2
Program: Technical Sessions
Time: 8:30 AM – 8:45 AM

Authors

Abstract

Understanding past climate is vital for predicting future environmental conditions, especially in Central Texas. Rapid population growth and extreme hydroclimate variability, exemplified by recent widespread droughts and flooding, make understanding regional climate critical for water resource management. In the Western US dry periods have become more frequent and intense. Concurrently, Texas’ rapidly growing population stresses already limited water resources, and pushes more people to live in flood-prone areas. In July 2025, the Guadalupe River rose 26 feet in 45 minutes, resulting in at least 135 deaths. Conversely, the droughts of 2011 and 2022 caused strict water use restrictions, billions of dollars in agricultural losses, and extensive wildfires. Current Texas water planning policy uses the 1950s drought as a planning benchmark, yet previous tree-ring PDSI reconstructions reveal similar or more severe droughts have occurred at least once per century over the past 500 years. To help understand longer term variations in precipitation and drought, and to contextualize regional differences in 21st century water deficit across the central Texas Hill Country, we developed an absolutely-dated, annual dendrochronological record from the Pedernales River Basin.  

We collected 39 bald cypress (Taxodium distichum) tree cores from the Pedernales River basin. Most trees included in this study were found in sheltered canyons of spring-fed tributary creeks to the Pedernales River. Ages range from 100 to 560 years (median: 164 years). 43% of the trees are younger than 170 years, which we hypothesize to be a result of historic 19th century logging in the Pedernales River basin and/or destructive floods. Total ring width, related to local moisture conditions, closely aligns with previous dendrochronologies from nearby Hill Country river basins. The 2006-2011 dry period is the most severe since the 1950s according to instrumental records, however, the most intense drought year of 2011 is not fully captured in the tree ring reconstruction. This insensitivity is likely due to a combination of the brevity of the most intense drought period, abundant fall precipitation in 2010, and the buffering effect of spring discharge. There is potential that similar intense but short droughts occurred in the pre-instrumental period, and total ring width chronologies failed to capture them in climate reconstructions. Future research will evaluate subannual growth variability to evaluate the intensity of short-term droughts.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414368

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